Busy all summer on installs, yet the bank account is emptiest when the diary is fullest

Written for plumbers, gas and heating engineers, electricians, heat pump and drainage firms, bathroom installers doing their own plumbing, and small multi-trade firms serving landlords, anywhere in the UK.

The short version

1. Map the next 13 weeks of cash.Put in when money really lands: service on the day, installs in stages, vouchers weeks after the job. Update it every Monday.
2. Wait for the issued voucher before ordering.An application is not a voucher. Take a deposit towards the goods, within any consumer code cap, and plan to carry the kit.
3. Invoice the day you finish, chase agents fast.Chase letting agents at 7, 14 and 30 days. When a slow payer offers more work, settle the old money first.

The year in this trade runs backwards for cash. Breakdowns and boiler swaps peak from October to February, and winter service work pays on the day. Summer is for installs, heat pumps, bathrooms and landlord certificate runs, and installs tie up cash in kit. A busy summer can leave you short just when the diary looks best.

A 13-week cash flow with your trade's real receipts

1. Service work.Paid on completion. Invoice the day the job ends and take card or bank payment at the door.
2. Installs.Deposit, stage payment and completion. Take a deposit towards the goods you order for that customer, kept within any consumer code cap. On a heat pump job that cap keeps the deposit small, so plan to carry the kit until the voucher is paid.
3. Service plans and landlord contracts.Monthly. Steady income, and part of what a lender reads.
4. Heat pump vouchers.In England and Wales, Boiler Upgrade Scheme vouchers are paid by Ofgem after redemption, weeks after the job; Scotland uses Home Energy Scotland grants and loans instead. Never fund an install on a voucher that has not been issued. A voucher lasts 3 months for air source and 6 for ground source: redeem it before it expires, or reapply with the owner's consent. As of Oct 2026, an off-gas-grid home replacing oil or LPG gets £9,000 until 31 March 2027, but never promise that rate before a voucher at that rate is issued.
5. Money going out.Wages, merchants on their account terms, van finance, insurance, scheme fees, VAT quarters and the tax diary. Update the whole sheet every Monday.

An application is not a voucher, and the voucher is paid only after you redeem it, weeks after the job. With the deposit capped, you carry the kit and the wages until then.

Know who pays slowly

Debtor days are trade debtors divided by credit sales, times 365. For example, £18,000 owed against £240,000 of credit sales a year is 27 days. Track it per customer: in this trade the risk sits with letting agents, builders and facilities management clients, not homeowners paying at the door. Chase letting agents at 7, 14 and 30 days.

When a slow payer offers more work, settle the old money first. For example, an agent owing £14,600 over 31 invoices on 90-day terms who offers you a 40-flat block: agree the arrears and 30-day terms in writing first, or price the credit into the new rates.

Funding the gaps

• Hire purchase or leasing for vans.
• Merchant accounts, often with a personal guarantee.
• An overdraft for the seasonal swings.
• Start Up Loans for new firms.

Lenders read two years' accounts, the order book and your plan income. Keep service, installs, plans and landlord work as separate tracking categories in Xero (or classes in QuickBooks) so you can see each one.

Asked in Greymill

Ask it about your own business

Paste this into Greymill with your own figures, and Cash & Profit works it through for your business.

More for plumbing, heating and electrical in the UK

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Open the interactive lesson · Every plumbing, heating and electrical lesson · What Greymill knows about the trade